Final answer:
An individual's filing status and gross income are the important factors for determining the requirement to file an income tax return.
Step-by-step explanation:
The important factors in determining whether an individual is required to file an income tax return are the taxpayer's filing status and gross income. According to the basic concepts of taxation, the requirement to file depends on the level of one's adjusted gross income and if this exceeds a certain threshold, which varies by filing status, one must file a tax return.
The decision to take itemized deductions may affect the amount of taxable income, but it does not determine the requirement to file. Therefore, the correct answer is c. The taxpayer's filing status and gross income.